Open Source Licensing Guide

Lately New Media Rights has been anxiously engaged in tackling various software licensing projects. For most developers, understanding open source licenses and the implications involved with using them can be fairly daunting. With these challenges in mind, we feel it’s worthwhile to provide a brief reference chart for developers considering open source licenses for their software.

This guide is by no means exhaustive but rather offers a valuable side-by-side comparison of the five most common open source licenses: GPL, LGPL, BSD, MIT, and Apache. While the guide is meant to help educate the public about open source licenses, developers should still consult licensing experts when choosing the proper licenses for their software.

All five of the licenses included in our chart allow commercial and derivative works, but each license differs in their language as well as in their attribution and source code distribution requirements.

The ‘BSD-like’ licenses such as the BSD, MIT, and Apache licenses are extremely permissive, requiring little more than attributing the original portions of the licensed code to the original developers in your own code and/or documentation.

The GPL license imposes similar obligations as the BSD-like licenses, but one major difference persists. The GPL license is ‘viral,’ meaning any derivative work you create containing even the smallest portion of the previously GPL licensed software must also be licensed under the GPL license.

It obviously follows that your clients will be obligated to release any derivatives of your GPL software under the GPL license. For those who are especially dedicated to the open distribution of their code and any future derivatives and use of source code the GPL can be a great license. While being the most widely used of the open source licenses, the viral nature of the GPL license can prove problematic for some commercial developers.

GPL licensed software, in exchange for keeping downstream uses open, prevents developers from releasing their own derivative programs under more restrictive licenses. This issue should be seriously considered prior to taking a dive into the GPL realm.

The LGPL license falls somewhere between being viral and permissive. LGPL licenses are generally used for software libraries, not programs; the most popular exceptions being Open Office and Mozilla. LGPL licenses are not ‘viral’ in the sense that you can dynamically link software programs to LGPL licensed libraries without licensing the software under the LGPL license, but as soon as you create a derivative of the LGPL licensed library or program you must use the LGPL license.

This exception does not exist under the GPL license. The NMR Open Source License Chart is attached below for your convenience. If you disagree with anything we have said here or in our chart, please contact us. We would love to hear your comments and considerations to make future improvements to this guide.

Each license is linked to its original location


GPL v3.0

LGPL v3.0


MIT (X11)

Apache v2.0

Can You Release Commercial Works?

Yes, but ALL source code must be distributed under GPL (viral).





Can You Create Derivative Works?

Yes, but ALL source code must be distributed under GPL(viral).

Yes, but any derivative software must be released under a LGPL license and allow reverse engineering for client modifications and debugging.





Must be included in your source code and distribution.

Must be included in your source code and distribution.

Must be included in your source code and any documentation that you include with the release of your software.

Must be included with your source code.

Must be included with your source code, and you may be required to include it in your distribution if your licensor requires.

So What?

The GPL dominates the free software world by significant margins. While it’s a favorite for those committed to the open source movement, many are shying away from it because of its viral nature which can potentially scare clients.

Not viral like it’s GPL counterpart. Software can be dynamically linked to other LGPL licensed libraries without having to release your source code under LGPL. This license is generally used for software libraries with exception of programs such as Mozilla and Open Office.

The BSD license is popular because of the flexibility it allows its licensees. There are really no limitations to what the licensee can do with the software other than the attribution requirements.

This is becoming a very popular license because of the extreme simplicity of its text. The whole license is about half a page long and is very permissive like the BSD license.

This license is somewhat similar to the BSD license, but goes into further detail in the attribution clauses and maintenance of intellectual property rights. Choosing this license over the BSD or MIT license is a matter of how specific you want your protections to be.



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